A plurality of uses for ladders or ladder elements is known from the state of the art, where the ladder or the ladder element is equipped with additional, supplementing structural elements so that special demands for each use can be met. An important problem in the design of ladders is the reliable setting up or placing of the ladder or of the ladder element. If a ladder is supposed to be utilized on a level, solid ground, problems with respect to setting the ladder up do not exist. Since, however, common use of the ladder requires it to be able to be set up on uneven ground, for example in order to carry out repairs on the outside of a house in order to maintain the outside or for other purposes, it is necessary to design the lower area of the ladder so that it is variable or adjustable in order to facilitate a setting up of the ladder in the vertical direction and to eliminate the risk of tipping. Similar problems exist when ladders must be set up on stairs, for example in order to paint staircases. It is known from the state of the art to provide the sidepieces of the ladder with suitable extensions in order to support, for example, one sidepiece on a lower step while the other sidepiece rests on the next higher step. However, the design of such a ladder is disadvantageous for specific applications, because the ladder stands on the two sidepieces, namely, the support distance corresponds with the distance between the sidepieces. In particular, in the case of a long ladder, there exists the danger that the ladder tilts laterally if it is set up slightly inclined or if the operator bends to the left or right of the central longitudinal axis of the ladder. In order to overcome this disadvantage, a cross member is known which can be fastened to the lower end of the sidepieces of the ladder. The cross member is wider than the distance between the sidepieces so that, as a whole, a safe support results. It is thereby disadvantageous that an adaptation to different heights is possible, or only a limited possibility, in the case of such a cross member since the cross member is usually fastened to the sidepieces of the ladder by means of a clamping device and must be positioned inclined at an angle with respect to the crosspieces of the ladder in order to compensate for an uneven ground. Such inclined positions, in turn, require a corresponding play of the clamping device or an inclined installation of the clamping device. This is not possible, or is only a limited possibility, for structural reasons, since the known cross member can compensate only for small differences in height.